A342365 The primes associated with A239800 (1 if A239800(n) = 0).

3, 17, 73, 337, 191, 709, 1289, 3137, 3313, 3181, 7349, 5449, 8243, 11621, 7681, 16673, 17477, 28657, 27893, 74441, 71023, 87869, 94439, 33889, 250301, 298013, 205957, 131489, 327179, 87961, 1178993, 354689, 1769791, 595817, 1304591, 417169, 2343359

Offset

1,1

Links

Jianing Song, Table of n, a(n) for n = 1..100

Formula

a(n) = 2*n*A239800(n)+1.

Example

The smallest m such that 2*m*i + 1 is not prime until i = 3 is m = 12, and the corresponding prime is 2*12*3 + 1 = 73 = a(3).
The smallest m such that 2*m*i + 1 is not prime until i = 4 is m = 42, and the corresponding prime is 2*42*4 + 1 = 337 = a(4).
The smallest m such that 2*m*i + 1 is not prime until i = 5 is m = 19, and the corresponding prime is 2*19*5 + 1 = 191 = a(5).

Prog

(PARI) isok(n, m) = for(i=1, n-1, if(isprime(2*m*i+1), return(0))); if(isprime(2*m*n+1), 1, 0)
a(n) = for(m=1, oo, if(isok(n, m), return(2*n*m+1))) \\ based on the conjecture that all numbers occur in A016014

Crossrefs

Cf. A239800, A016014, A070846, A342364.

Sequence in context: A049181 A248917 A282400 * A179596 A339647 A191587

Adjacent sequences: A342362 A342363 A342364 * A342366 A342367 A342368

Keyword

nonn

Author

Jianing Song, Mar 09 2021

Status

approved